A spanner is a generally used tool for rotating a nut or other part. An adjustable spanner (i.e. a movable spanner) has been used in the prior art. These spanners are disclosed for example in Taiwan Patent Publication Nos. 251500, 257126, 274755, 302793, 304909, 308925, 310647, 312187, 312188, and 340437.
However, prior art adjustable spanners only have two surfaces for engaging contact with a nut so that often the nut cannot be clamped tightly. This requires a larger force than necessary to clamp the nut. Consequently, the edges of the nut may be destroyed, effectively rendering the nut useless, as it cannot then be locked tightly or released.
Moreover, nuts are sometimes located in a cramped space (as shown in FIG. 1). Yet, a prior art spanner 10a, during operation, is engaged to the nut 11a in a first position A, then rotated to a second position B. The whole spanner 10a is thereafter pulled out of engagement with the nut 11a and returned to the first position A for repetition of the process. Therefore, the operation is time consuming.